Production of motor-fuel hydrocarbons



July 23,` 1946. F, E FREY 2,404,483

PRODUCTION .OF MOTOR-FUEL HYDROCARBONS `ATTORNEYS Patented July 23,1946v RoDUcT'IoN oF MOTOR-FUEL HYDRooARBoNs Frederick E. Frey,Bartlesville, Okla., assigner to Phillips Petroleum Company, acorporation of Delaware Application March 12, 19424, Serial No. 4311.429

This invention relates to the conversion of hy drocarbons. Moreparticularly, it relates to the production of motor-fuel hydrocarbonsfrom relatively low-boiling hydrocarbons by a process in whichhydrofluoric acid is used as a catalyst. application is acontinuation-in-part of my copending application, Serial No. 426,627,filed J anuary 13, 1942, and Serial No. 432,679, filed February 27,1942. f Y

An object of this invention is to convert relatively low-boiling normalparain hydrocarbons, such as normal butane and/or normal pentane, tohigher-boiling saturated hydrocarbons.

Another object of this invention is to produce a motor fuel stock fromrelatively low-boiling paran-ins by a process in which used hydroiiuoricacid catalyst from an alkylation step is used as a catalyst foris'omerizing normal paraiiins to isoparaflins suitable for use in thealkylation step.

A specific object is to combine, in a process for converting normalbutane to motor fueljan isomerizing step with an alkylating step in sucha Way that the material charged to the alkylating step is substantiallyfree from normal parafns.

Another specific object is to produce a motor fuel of high octane numberin increased yield and of increased volatility as compared to that whichis produced by ordinary alkylation processes.

A specific object of this invention is to produce a motor fuel stockfrom relatively low-boiling parafflns by a combinationisomerization-alkylation process in which an azeotropic mixture ofhydroiuoric acid and an isoparaliin is distilled from the elluent froman isomerizing step and is passed to an alkylating step.

Other objects and advantages of this invention will be apparent from theaccompanying description and discussion.

Isoparafns of relatively low molecular weight, such as isobutane andisopentane, can be reacted in the presence of an alkylation catalyst,such as concentrated hydroiiuoric acid, at a comparatively low reactiontemperature, for example, in

' the range of 0 to 200 F., With alkylating reactants such as oleiinshaving 3 to 5 carbon atoms per molecule and corresponding alkylcompounds such as alkyl halides, alcohols, ethers, esters, and the like,preferably those of secondary or tertiary structure, to producehydrocarbons in the motorfuel range which have high antiknock values and-that are suitable for use in aviation gasoline.

Normal paraflins, such as normal butane and normal pentane, can, alsolbe alkylatedbut only under considerably more drasticv conditions, sothat 9 Claims. (Cl. 260f-683A) n the product usually is of lower qualityin respect to octane number and is produced in lower yield than thatobtained by alkylating the corresponding isoparains.

In such alkylation processes, the hydrouoric acid eventually becomes sospent or deactivated by acid-'soluble and/or nuoro-organic by-pred'-ucts that it is unsuited for continued use; the spending or deactivationis especially rapid at elevated temperatures, such as those required forthe alkylation of normal parailins, Disposal of the spent acid is aconsiderable problem, be cause of the corrosive nature of the acid;furthermore, heretofore no use for the spent acid has been known, sothat in the past it has been necessary to provide `acid-recovery steps,such as distillation to recover the free hydrogen fluoride, and thermalldecomposition and distillation to liberate and recover the organically combined fluorine as hydrogen fluoride.

The product obtained by catalytic alkylation usually consists of primaryalkylation products, for example when alkylating isobutane withbutylenes the product usually consists predominantly of octanes withrelatively small proportions of low-boiling hydrocarbons such aspentanes and hexanes. Because of this fact, it is usually' necessary toincrease the volatility of the prr'aduct,` so that it may be'efficiently used as in aviation gasoline, by adding-additionalrelatively low-boiling hydrocarbons, stitch as lsopentane and branchedhexane's.

I have now found that spent or partly deactivated hydroiluoric acid froman alkyl'ating step can be advantageously used as a catalyst inA anisomerizing step to convert relatively low-boiling normal 'paraflinssuch as normal butane and/or normal pentane, into isop'araflins, such asisobutane and/or i'sopentane, that are suitable for' con' version to`motor-fuel hydrocarbons in the alkyl'- atin'g step. .I have also foundthat appreciable proportions of motor-'fuel hydrocarbons are' formed bysecondary reactions 'in this isomerizing step, and that thesehydrocarbons can be advantageously added to the product of the al-vkylating step to increase the yield and the volatility ofaviation-'grade motor fuel. Further, I have found that from the effluentfrom suchV a conversion can be distilled. a low-boiling or'azeotropic'mix'ture comprisingv isobutane and hydrogen fluoride, which'is' suitable for use as feed material to' an alkylating. stepl In onespecic embodiment, for example, the present invention comprisesisomerizin'g normal butane by' the ison'ieriz'ingv action of hydroflor'cl alkylation catalyst.

acid previously used in an alkylation step, using the resultingisobutane for conversion to motor- V fuel hydrocarbons by hydrouoricacid-catalyzed alkylation, and combining the products boiling above thebutane range in such manner as to l obtain a motor fuel of desirablyhigh anti-knock rating and volatility-` L An advantageous feature of myinvention is an azeotropic-distillation step, interpositionedy betweenan isomerizing step and an alkylating step,

for separating isobutane and lighter hydrocarcarbons.

ment. The resulting overhead mixture comprises, as well as isobutane, asubstantial proportion of hydrouoric acid in a relatively'ative andanhydrous condition2 in which it i'ss'u'itabl' for use as catalyst in analkylating step; this l overhead mixture is'advantageously chargeddirectly to the alkylating stepwith no prior treatment other thancondensing andcoolingto a suitable temperature.

Another advantageous feature o f-.my invention l is the blendingoflow-molecular-weight.normally 1 liquid hydrocarbons, chieflyisopentane'and iso-f' merio hexanes, which areproduced by sideI and Ysecondary reactions inA an isomerizing stepwith the'` alkylate producedin an alkylation step to increase the volatility of the alkylate.`lThese low-molecular-weight normally liquid hydrocar--l bons arepreferable Vto natural-gasoline fractions of a correspondingboilingrange, which are sometimes blended in motor fuel to increase itsvolatility, because they -comprise relatively larger bons from vnormalvbutane and heavier"hydro-gL By this particular step, an eflcient'"separation of isobutane from normal, butanejs" effected with a minimumof .-lfractionating' equipproportions of branched-chain para'ins andV Y1hencehave higher octane numbers than vthose I of the" natural-gasolinefractions.V 1; All understandngbflsme; aspects of my in-v vention maybeaided by a considerationof ,the

accompanyingdrawings, in which Figure 1 isa l schematic-flow-diagram ofone arrangement for practicingthe invention and Figure 2 aschematicflow-diagram. 0f another arrangement for which is passed through valveI3 and conduit I4 to alkylator I5, and .into anormal butane.r fraction,which is passed through valve I6 and con- `duitI'I to pump I8; Y 1 Inalkylator I5, the isobutane is mixed .under alkylating conditions withan alkylating reactant,

and valve 22 and/or through conduit .In the composite feed toalkylator'l 5, the `weight ratio of -isoparaiflns to olefins, orAotherxalkylatin'greactant, preferably is in the range of 2:1 to 20:11.

i or more, andthe-weight ratioof hydrofluoric acid l to totalhydrocarbons preferably is in the range.

012:1 toz4z1. The olefin preferably isxntroduced :into the reactionmixture under conditions of high .turbulence and/or in multipointwise.fashion, so that it' is rapidly mixed and diluted vwith the isoparafnreactant. .z Thisprocedure iseadvantageous in order to favor the desiredolefinisoparain junctures, or alkylation reactions, and to hinderundesirable olefin-olefin junctures, or polymerization reactions.Preferred operating conditions in alkylator I5 are a temperature in therange of 30 to 150 F., a pressure sufficient to maintain allcomponentsin the liquid phase,- and a' reaction'time of about' l'to 30 or 'moreminutes; but if desired other conditions may be used in iparticularcases without passing beyond the scope of this invention.

' ',TheJjres'ulting mixture passes through conduit 25'having valve 26 toseparator 2l, wherein it is separated'into two liquid phases as bycooling and gravitational or centrifugal means.

The heavier or hydroiluoric acid phase is passed through valve 28, andconduit 29 to pump 30. If

i desired, however, part of the acid may be recycled ably also, whenthere is'some excess propaneand incidental diicultly condensible gases,such as methane and ethane, part of the debutanizer overhead is passedthrough valve 40 and conduit 4I to depropanizer 142, from which thesegases are passedthrough valve 46 to separator 16, and from which theresulting 1 concentrated butanes are passed to fractionator I0throughvalve 41. A normally liquid kettle product fromdebutanizer 35 ispassed through valve 43 and conduit 44 to rerun column wherein it isseparatedinto two fractions: (l) a major motor-fuel fraction comprisinghydrocarbons suitable for Yuse in aviation gasoline, which is withdrawnthrough outlet 48 having valve 49, and (2) a bottom fraction comprisinghydrocarbons boiling above Vthe motor-fuel range, which is withdrawnthrough outlet 5.0 having valve 5|.' v v Normal butane from frac'tionator I0 and hydrofluoric acid from separator'21are forced bypumps I8 and 30, respectively, through heating coil 52 to reactor 53,wherein the normal butane is isomerized to isobutane to afsubstantialextent.

If desired, additional normal butane may be ad- V portions of spent acidfrom separator 21 that pass through valves 28 and 3|, respectively.

The temperature in ,reactor 53 may be within the range of about 250 to1000 F. A temperature inthe range 400 to 800 F. is usually preferred;

at low temperatures the rate of reaction is low, and at hightemperatures some cracking and carfor reasons of economy in equipmentand oper-- ating costs, to use a pressure inthe range of 250 to'2000pounds per square inch. The reaction time may be within the range ofabout 1 to about' 300 minutes depending chiefly upon the temperature;the time required decreases with increase in temperature. If thereaction time is very short, such as 1 to 5 minutes, the reaction can becompleted in coil 52 or an .extension thereof; whereupon reactor 53 maybe by-passed orremoved from the system by means not shown. Preferably,the reaction zoneispacked with a contact mass, such'as steelturningsyalumina, bauxite, or other material resistant to corrosion byhydrofluoric acid and suitable for promoting the reaction and/or heat`transfer.

' The resulting mixture from reactor 53 is passed through valve 56' andconduit 51 to separator 58, wherein it is separated into two liquidphases as by cooling and gravitational or centrifugal means.

, Although the heavier or hydrofluoric acid phase. from separator 58 maybe recycled to coil 52 and/ or alkylatcr I 5as through valve 59 and/orvalve 60, at least a part of it is preferably passed through valve 6|and conduit 62 to `iractionator 63. In'this fraction tor it is separatedinto (l) an overhead fraction comprising substantially anhydroushydrofluoric. acid, which is passed through valve 64 and conduit 23 toalkylator I5, and (2) a bottom fraction, or sludge, comprisingacid-soluble materials, which maybe withdrawn through valved outlet 65.

The lighter or hydrocarbonphase from separator 58 may bel passed throughvalve-63 and conduit 31 to fractionator Il); however, in order toYrecover valuable normally liquid hydrocarbons produced in theisomerizing step .by secondary reactions, it is preferably passedthrough valve 61` and conduit E8 .to debutanizer B9, wherein it isseparated into fractions, The overhead fraction, which comprisespropane, normal butane, and isobutane, and generally some hydroiiuoricacid, is passed through valve 10 and conduit 1| todepropanizer A4,2; thebottom fraction, which comprises isopentane, hexanes, and otherhydrocarbons, maybe withdrawn through outlet 12 having valve 13, but ispreferably passed, at least in part, through valve 14 and conduit V15,together with normally liquid alkylation products from debutanizer 35,to rerun column` 45.

In separator ,16. hydrofluoric acid is separated as a liquid phase fromthe depropanizer 42, as by cooling and gravitational means. The acid maybe withdrawn .through valved outlet 11, but/preferably is recycledtoalkylator I5` or coil 52 by 4 pane and vother light gasesare withdrawnthrough valved outlet 18. A part or all of the` propanecontainingfraction removed from the top of depropanizer 42 may be passed directlyto the isomerization step :through conduit 8D, controlled by valve 8|,to conduit I1 and heater y52.

Referring now to Figure 2 a suitable hydro-iv carbon material, such asamixture comprising chiefly normal paraiiins, preferably normal butane,is admitted through inlet ||I, valve I I2, and pump `||3. To thishydrocarbonfmaterial is added hydrofluoric acid previously usedin thealkylation step, from acid-recycle conduit |46, by pump Il 6; ifdesired, additional acid may be admitted throughinlet ,l I4 and valvev|-|5. The resultant acid-hydrocarbon; mixture is ypassed through heateri|1 to reactor. I I8.4 The -oper-A ation of heater I I1and reactor,`IIS. ,are-.,substan,

tially as described for heater 52 and reactor 53.

overhead fraction from lighter or hydrocarbon phase is .The resultingvmixturein'reactor IIS is passed through valve ||9 and conduitl |2D.topartial condenser I2I, wherein, by a suitable cooling means, relativelyhigh-boiling material, such as hydrocarbons Vboiling :aboveapproximately the pentane range, heavy hydrofluoric acid-solublematerial, and the like, are condensed or liqueed. Suitable conditions inpartial condenser I2 I i are a temperature in the range of 125 to 400 F.and a corresponding pressure in the range of 15 to 400 pounds per squareinch. The optimum conditions. are readily determinable by trial and/orfrom well-'known vapor-pressure relav tionships. of the variousconstituents. Conditions'outside the. ranges given above may be.

used, if-desired or necessary for any particular case. 1

The Vresultingpartly liquefied mixture from partial condenser |2| ispassed through conduit |221. and valve |23to separator |24, wherein itis separated into a gas phase and a liquid phase.

The temperature and the pressure. should bev as nearly as possible thesame as those in partial condenser |2I. The liquidphase which comprisesmainly hydrocarbons and acid-soluble substances boiling approximately inthe hexane range and above, is Withdrawn through valved outlet |25. Thegas phase is passed through valve |23 andconduit |21 to condenser |28.

In condenser |28, the gas phase from separator |24 iscooled andliquefied. The resulting liquid mixtureV of acid and hydrocarbon phases,which comprises hydrofluoric acid, isoparaiiins, and unreacted normalparaiiins, is passed through Valve |29"v and conduit. |30 Vtofractionating means ISI.

'Two fractions are withdrawn from fractionatin'g means |3I'. The4overhead fraction, which comprisesl a low-boiling azeotropic mixture ofhydrofluoric acid Iand isobutane, and. usually some lower-boilingmaterial such as propane, is passed through valve |32 and conduit |33 toalkylator |34. The bottom product, which comprises hydrofluoric acid andhydrocarbons boiling above isobutane, rmay be recycled in part throughAvalve |35 and conduit |36 to coil II1; preferably, however, most of itis passed through valve |31 and conduit |38'to separator |39.

In separator |39 the kettle fraction from frac- `tionator |3I isseparated into two liquid phases.

as by cooling andy gravitational means. The passed through valve |40 andconduit I4Ito debutanizer |42. The heavier'or hydrofluoric acid phasemay be passed in part through valve |43 and conduit |44 for use ascatalyst in alkylator |34, but pref-k erably most or all'of it isrecycled through valve |45 and conduit |46 to pump |I6.

In alkylatorV |34 the overhead mixture comprising hydrouoric acid and`isobutanle from fractionator |3I is mixedv under alkylating conditionswith an .alkylating reactant, such as an olefin having from: 3 to 5lcarbon atoms per molecule, or'anequivalent alkyl compound, which isintroducedthr'ough inlet |41 and valve |48. Since the overhead mixtureusually contains insufficient hydrofluoric acid'for effecting withdesirably high emciency. the alkylation ofthe isobutane, additionalalkylation catalyst is admitted through inlet |49l and valve |50 and/orthrough conduit |44. Such additional alkylation catalyst may be any ofthe alkylation catalysts that are operative in the presence ofhydrofluoric acid,

Vbut for the sake of simplicity and' of eliminating otherwise necessarysubsequent catalysttional i hydrofluoricv acid, which, is. preferred.

Usually the hydrouoric `acid admittedrthrough` inlet |49 may be the solevcatalyst; feed to thel system. In the feeds toalkylator |34 the weightratio of isobutane toV olefin, or other alkylating re' actant, ispreferably in the range of 2:1 to 20:1

i or more, and the weight ratio of hydrouoric acid tototalhydrocarbonsis preferably in `the range 0.2:1 to 4:1.. The olen ispreferably inl troduced into the reaction mixture Vunder conditions of 1high turbulence Vand/,or in .multipointwise fashion,so that it isVrapidly mixed This .procedure .is advanpolymerization reactions.Preferred operating l conditions in alkylator |34 are a temperature in,

the range of 30 to 150 F., a pressure suflcient to maintain allcomponents in the liquid phase,

q and a time ofaboutV 1 Vto 30 orV more minutes; l however, conditionsoutside of these ranges may alsobe used in particular cases withoutpassing beyond the scope of this invention.

The resulting mixture passes through conduit i |5| and valve |52 toseparator |53,\wherein it is separated into two liquid phases as bycooling and gravitational or centrifugal means.

Part of the heavier or hydrofiuoric acid phase maybe recycled throughvalve. |54, conduit |55, "and .pump |56 to alkylator v|34;preferably anamount. of acid approximately equivalent toor Y lsomewhat greater than,that introduced to the lallfzylator in the overhead fraction fromfracltionator |3| is passed through valve V|51 and `conduit |46 to pump||6 for use in thejsomerizing step. VIt is a particular feature of thisin# isomerization reaction is Ya hydroiluoric .acid

, which is discharged from the alkylation step asA spent alkylationcatalyst. The lighterv or hydrocarbon phase from separator |53ispassedthrough valve |58 and conduit |59 to fractionating means |60, inwhich.

tion of highly branched parainic reaction prod-V ucts boiling within themotor-fuel range, whichA iswithdrawn through outlet1|65 having `valve|66; Vand (4) a relatively high-boiling hydrocarbon residue, which isWithdrawn through outlet |61 having valve |58. ...Preferably to increasethe over-all yield, part of the propane-rich low-V boiling fractionisrecycled through valve 69'and conduit to coil |.|1 of the isomerizingstep.V

`In separator |63, by cooling and gravitational means, a liquidhydrouoric'acid phase is sepa-V rated Yout. This hydrouoric acid phasemay be withdrawn through valved outlet |1|, or itV may be recycled to'alkylator |34 or to coil ||1 by means not shown in the drawings. carbonresidue (gas and/or liquid) is withdrawn through valved outletY |12 and.disposed of in any suitable manner.

In debutanizer V|42 the hydrocarbon phase'from separator |39 isseparated by distillation into .two` fractions. f Thejoverhead fraction,which' comprises mostly fno'rmalbutane 'with' some lhydro-.-

' vention that the catalyst used for effectingth'eKY l. motor-fuelhydrocarbons anda vbottom fraction recover hydroiiuoric acid,

fluoric .`acid,' is recycledthrough valve |13 and conduitI14tothe`isomerizingrstep." The bottom fraction;v which. comprises.rlow-boiling normally liquid hydrocarbons, such'as isopentane, hexanes,and heptanes, maybe. Withdrawn through outlet |15 having valve 16;preferably, however, atleast ai part vof it is passed through valve |11and conduit |18 Vto fractionating means |60, wherein it becomes'blended'with the liquid alkylation prod.

A fejw'of the many aspects'of my invention are illustrated bythefollowing' examples, `which are illustrative, but notnecessarilylimitative;of the invention.

' Y "Eamplel' In an arrangement similarto that illustrated in Figure. 1,`a mixture ofl approximately equal proportions of "normal butane andisobutane' is charged to a fractional-distillation column, from.

Whiclr an overhead fraction consisting chiey of i'sobutane is passed toan alkylation step, and from which y a bottom fraction consistingrchieiiy of normal butane is passed to an isomerization'step. Butylenesand concentrated hydrofluoric acid are separately charged to thealkylation step. In this alkylation step, conditions are approximatelyas follows: temperature, F.; pressure, 125 pounds per square inch;reaction time, 6 minutes; isobutane-to-olen molal ratio (inthegmaterials entering the" alkylation reactor), 10:1; hydrocarbon-toacid weight ratio, 1,5:1; .and rapid mixing to maintain intimate contactbetween the acid and hydrocarbon phases.

Y The resulting eiiiuent fromV the alkylation step is separated bygravity intoA two liquid layers. The heavier or acid layer is passedto'the isomerization step. The lighter orv hydrocarbon layeris` tion,vcomprising normally liquid hydrocarbons,`

is passed Vto a rerun column. In theisomerization step, proximately asfollows:

temperature, 500 F.; pressure, 750 pounds per square inch; time, Y4.5

minutes;j hydrocarbonp-to-acid ratio, about 1:1 f t byweight; and acontact mass comprising steelk turnings in the reactor.

The eiiiuent from the isomerization step' isl cooled and separated intotwo liquid phases. The heavier or acid phase'isfractionallyV distilled'to which is returned to the alkylation step. The lighter or hydrocarbonphase is also fractionally distilled; it has a hydrocarbon compositionabout "by weighty propane, 10;

butarie, 51.; pentanes (mostly isopentane), 10;` hexanes, 3. AnVVazeotropic mixturejof propaneA as follows, inper cent isobutane, 26;normal and hydrofluoric acid is ization* step;

recycled to the yisomer- In thevrerun column, themixture of normallyliquid hydrocarbons fromboth the alkylation and lthe isomerizationsteps` is fractionally distilled toyield an overhead fraction ofaviation-range of higher-boiling hydrocarbons. The yield of motor-fuelhydrocarbons is about 205 per cent byV Aber of about 91 and a desirablyhigh volatility'. v

conditions are ap-k the excess propane'is withdrawn from the process;the isobutane is passed to the .H495 1 Example II l In an arrangement-`similar tothat illustrated in Figure 2, normal `butane and concentratedhydrofluoric acid are charged to an isomerization Stage. The isomerizingconditions are approximately as follows: temperature, 425 Eg-pressure,2000 pounds per square inch `(mixed-phase or liquid-and-gas conditions);reaction time, 60 minutes; acid-to-hydrocarbon ratio, 1.521. Theresulting isomerization eiiiuent comprises a hydrocarbon mixture ofapproximately `the following vcomposition, in per cent by weight.:propane, v; isobutane,'26; normal butano,l 51; hydrocarbons boilinghigher than normal butane; 13. f l

. From the isomerization efliuent is Withdrawn, by partial cooling andgravitational settling, a liquid product which comprises substantialproportions of'fpentanes and hexanes.l The" remaining material is passedto a fractionator from the bottomcf which amixture of hydrofluoric acidand hydrocarbons (mostly normal butane). boiling above isobutane isrecycled to the isomerizing stage, and from thetop" of which alow-boiling the'iso'butane, is introduced as alliylating reactant intothe alkylator.

rThe conditions in the alkylator are as follows: temperature, 95 to 125EL; pressure, 150 to 200 pounds per square inch; average reaction time,i minutes; and rapid agitation to maintain intimate contact between acidand hydrocarbon phases. f

The resulting efiluent mixture from the alkylator is passed to a settlerin which it is separated into an acid phase and a hydrocarbon phase. Ofthe acid phase, a proportion equivalent to that passing from theisomerizing stage to the alkylator is recycled to the isomerizing step;the remainder is recycled to the alkylator. The hydrocarbon phase ispassed to a fractionating means, from which are obtained variousproducts and recycle fractions, such as those indicated on the drawingsas being obtained from fractionation means 160. The motor-fuel fractionhas a clear octane number of about 90 and is suitable for use inaviation gasoline. f

There are numerous modifications of my invention, which will be obviousto those skilled in the art of hydrocarbon conversion. For example, ifthe paraiiinic feed materialr comprises normal paraflins butsubstantially no isoparains, it is advantageously admitted in themodification of Figure 1 to the isomerizingstep through inlet 5f?. andValve 55 instead of to fractionator It through inlet Il and valve l2.Also, if desired, in order to inhibit the formation of low-boilinghydrocarbons in the isomerizing step, a propane-rich fraction,

10 hydrofluoric a`cid.-. Some change in the' flow scheme that Willbe-obvious `to those skilled-in the art may be advantageous tofacilitate the use of such modiers. Y

Additional pumps, valves, conduits, coolers, fractionators, and otherequipment, such as are well-known in the art of hydrocarbon conversion,may be used Wherever they are necessary orconvement for obtaining theresults indicated in any particular case. The scope of my inventionshould v not b'e unduly limited by specific numerical values recitedherein. -l y' Iclaim: ,Y '-f "11. A process' yforiproducing'niotorJ-fuelhydrocarbone,Which"cmprisesr yisoii'e'riZirig a; lowboilingl normalparaiin Yof `four Eto yiii/e carbon atoms per `molecule in 'the'."presence of concentrated hydrofluoric acid in anf -i'somerizat'ionstep; separating the eiliuent from said is'omeri'z'af vtionisft'ep bydistillation intoI an overhead fraction compri'singihydrofluorc acid andan isoparafiin of four to five carbon'at'orns per mt'plecule,V` and intoafbo'ttoinfraction comprising hydroiiuoric acid and a normal paraflinhaving 'fourtoiive carbon atoms per molecule passing sa'id bottom Yfraction to said isomerization step; 'passing said parafn is normalbutane. Y i i such as that from the top of depropanizer d. mai7 berecycled to coil 52 through conduit 80 and valve 8l. Various catalystmodifiers that do not enter the alkylation reaction under the prevailingconditions, such as organic or inorganic 4. A process forproducing vanormally liquidy isoparaflinic hydrocarbon lmaterialboiling in the Ymotor fuel range from lower-boiling normal parafn hydrocarbons of atleast four carbon atoms per molecule, which comprises subjecting such anormal paraflin to catalytic isomerization in the presence ofhydrofluoric acid as the isomerization catalyst to produce low-boilingisoparaflin hydrocarbons, separating from effluents of saidisomerization used hydrofluoric acid catalyst and an isobutane fractionand a volatile normally liquid hydrocarbon fraction boiling in the motorfuel range, reacting said isobutane fraction with butenes underalkylation conditions and in the presence of said yused hydrofluoricacid catalyst to produce irsoparafns of higher molecular Weight and inthe motor fuel range, separating an isoparaflinic hydrocarbon fractioncomprising `pyredominantly isooctanes so produced, andblending saidisooctane fraction and said volatile liquid hydrocarbon fractionseparated from the isomerization step to produce a composite motor fuelproduct.

5. A process for producing normally liquid isoparaflinic hydrocarbonsfrom a loWer-boilingnormal parain hydrocarbon of at least four carbonatoms per molecule which comprises subjecting such a normal paraiin inan isomerization step to catalytic isomerization in the presence ofhydroiluoric acid as the isomerization catalyst to produce low-boilingisoparaffin hydrocarbons, subjecting effluents of said isomerization tofractional distillation to produce a 10W-boiling fraction containingisobutane and hydrofluoric acid and a higher-boiling fraction containinglowboiling normal paraflins and hydrofluoric acid, returning saidhigher-boiling fraction to said isomerization step, passing saidlow-boiling fraction toY analkylationstepand reacting isobutane con#tained therein with an alkylating'reactant in the presenceof hydroluoricacid as -the'lalkylation catalyst to'produce isoparafiins of highermoleculanweight, and recovering a hydrocarbonfraction containing higherl boilingisoparaflins Vso produced.

- 6. VThe process of claim 5 in which atleast a portion of the spenthydroiluoric acid alkylation catalystV is passed to the isomerizationstepas the isomerization catalyst. l i

'7. Aprocess for producing an isoparaiiinic mo- Ytor Yfuelstockfcontaining both low-boiling and high-boiling isoparanichydrocarbons from low-` boiling normal paraiilns, which comprisessubyjectingsuch anormal paraiiinto catalytic conversion in the presenceof hydroiiuoric acid asthe conversion catalyst to produce isobutane and'10W-v boiling.- normally liquid isoparafns, separating from ellluents ofsaid conversion a mixture Y'coni tainingvsubstantial quantities ofyisobutane andv substantiallyanhydrous hydrofluoric acid, sep'-aratinglalso a vlow-boiling liquid isoparanic hy` drocarbon fraction.adding to said isobutanef.

hydrouoric acid-mixture lan alkylating reactant land' subjecting -thecomb-ined mixture to alkylav tion conditions Ato produce high-boilingnormally liquid isoparaiins boiling in the-motor fuel range,separatingvfrom eflluents of said alkylation spent hydrofluoric acidcatalyst and passing-at least so formed, and blending the last saidhydrocar- V and a normally liquid lay-product fraction; re-V asubstantial portion of same toV said -converl sion, separating-also fromveilluents of said alkylation a normally liquid isoparanicvhydrocarbonfractioncontaining said high-boiling isoparamns fraction with normalbutane; subjectingthe re.

sulting acidebutane rmixture to V"such" conditions in an isomerizationstep thatY said normal butane is isomerized to isobutane to'asubstantialextent by hydrofluoric acid; separating lfrom the resulting eilluentfrom `said isomerization step used hydrofluoric acidcatalyst and anisobutane fraction, an unreacted vnormal butane Nfraction,

cycling said unreacted'normal Vbutanefraotion to said isomerizationstep; passingsaidused hydrofluoric acid catalyst, said unreactedilsobutane fraction and Vsaid isobutane fraction 'toi said alkylationstep; mixing together "said normally liquid hydrocarbon fraction e andlsaid Ynormally liquid llay-product fraction; separating from theresulting normally liquid mixture a motor-fuel fraction;v andwithdrawing from the process said Imotor-fuel fraction.

,9. The process of claim 8 in which is at least one butylene.

said oiefin FREDERICK E.

